Zuke is a technique of marinating lean red tuna meat in a mixture of three parts dark soy sauce, one part mirin, and one part sake. In the Tenpo Era (1830-1844) when sushi was first served in restaurants, zuke was used as the method of preservation. It is still enjoyed today for the flavor it brings. Before marinating the fish it must be scalded with hot water to harden the surface and prevent the marinade from penetrating too deeply, thus maintaining the freshness and flavor of the meat.